For example, as a wiper motor for an automobile, a 3-brush type motor capable of changing a rotation speed is used. In such a motor, an armature on which an armature coil is wound is rotatably disposed inside a cylindrical yoke including a plurality of magnetic poles formed at an inner circumferential surface thereof. The armature has the armature core fitted and fixed onto a rotation shaft, and a slot elongated in an axial direction is formed in the armature core. In the slot, a wire is wound through a distributed winding method at predetermined intervals to form a plurality of coils. Each of the coils is electrically connected to a segment of a commutator attached to a rotation shaft.
Each of the segments can come in contact with the brushes. The brushes are configured of three brushes, i.e., a low speed brush, a high speed brush, and a common brush commonly used for these brushes. The high speed brush is disposed to be angularly advanced more than the low speed brush. Then, power is supplied by the common brush and the low speed brush during normal operation, and supplied by the common brush and the high speed brush during high speed operation. According to the above-mentioned configuration, the 3-brush type motor can set a difference in the numbers of effective conductors between during normal operation and high speed operation. That is, in high speed operation, the motor is more angularly advanced than in normal operation, and is operated at a higher revolution speed than in normal operation.
Here, a motor such as a wiper motor or the like mounted in a vehicle normally requires miniaturization due to requirements of improvement of vehicle mountability or the like. For this reason, for example, a motor in which the number of slots of the armature core is set to 16 and the number of magnetic poles is set to 4 is disclosed. In the motor, a coil is wound to straddle over four teeth according to the number of magnetic poles through a distributed winding method. Then, the coil is connected to a commutator having sixteen segments in which the same electric potentials are short-circuited (for example, see Patent Literature 1).